1. Field of the Invention
The invention relates to a pump apparatus and, more particularly, to a pump apparatus having a water pump function which is disposed in a cooling system of a vehicle internal combustion engine.
2. Description of the Related Art
Generally in a cooling system of a vehicle internal combustion engine (hereinafter, simply referred to as “engine”), cooling water of the engine (a cooling liquid whose main component is water) is circulated by a water pump, and when the cooling water temperature is high, the cooling water is cooled by a radiator, and when the cooling water temperature is low, the amount of flow of the cooling water that passes through the radiator is restricted by a thermostat. In the engine cooling system, there is often provided a pump apparatus in which a thermostat disposed near a water pump is incorporated into a major member of the water pump. In such a case, the thermostat is incorporated into, for example, a pump housing of the water pump, and is fixed at a predetermined position by fastening the pump housing to an engine block, or is incorporated into a cylindrical water inlet member that forms a suction passageway of cooling water to the water pump, and is fixed at a predetermined position by fastening the water inlet member to a water pump housing that is integrated with a chain cover (chain case).
Known pump apparatuses of this kind are, for example, a pump apparatus in which a pump housing and a chain case are integrated, and entry and exit passageways of cooling water and a bladed wheel chamber as well as a temperature-responsive portion-housing hole of a thermostat are formed in the chain case (e.g., see Japanese Utility Model Application Publication No. 01-85419 (JP-U-01-85419)), and a pump apparatus in which an inlet pipe, a thermostat housing portion, an impeller chamber and a swirl chamber are integrated with the pump housing (e.g., see Japanese Patent Application Publication No. 09-13966 (JP-A-09-13966)). Furthermore, a pump apparatus in which a suction passageway, a thermostat housing portion and a pump housing portion are formed in the pump housing that is fixed to an engine cylinder head and a thermostat entry-side lid is integrated with a pump lid (e.g., see Japanese Patent Application Publication No. 04-284122 (JP-A-04-284122)).
However, in the pump apparatuses as described above, a recess portion that houses a pump rotor, such as a centrifugal pump impeller or the like, and that defines a swirl chamber or the like is formed in the water pump housing, so that it is necessary to provide a cover that covers the opening of the recess portion and that has a bearing hole for the pump rotor, and an inlet member that forms a cooling water suction passageway on a bottom side of the recess portion, separately from the pump housing. Thus, the housing of the water pump in the related art has a three-division structure whose main component parts are divided into three parts.
Therefore, a plurality of large gasket seals need to be provided in connecting portions between these main component parts of the housing, thus leading to an increased cost of the pump apparatus. In addition, even if sub-assembly, such as the incorporation of a thermostat or the like, is performed, it is necessary to perform an operation of attaching a plurality of large gasket seals, and therefore it is not easy to reduce the number of man-hours for assembling the engine.